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timknip/setFromRotationMatrix.js

Created August 18, 2011 16:54
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Quaternion setFromRotationMatrix
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setFromRotationMatrix.js
setFromRotationMatrix: function ( m ) {
// Adapted from: http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm
function copySign(a, b) {
return b < 0 ? -Math.abs(a) : Math.abs(a);
}
var absQ = Math.pow(m.determinant(), 1.0 / 3.0);
this.w = Math.sqrt( Math.max( 0, absQ + m.n11 + m.n22 + m.n33 ) ) / 2;
this.x = Math.sqrt( Math.max( 0, absQ + m.n11 - m.n22 - m.n33 ) ) / 2;
this.y = Math.sqrt( Math.max( 0, absQ - m.n11 + m.n22 - m.n33 ) ) / 2;
this.z = Math.sqrt( Math.max( 0, absQ - m.n11 - m.n22 + m.n33 ) ) / 2;
this.x = copySign( this.x, ( m.n32 - m.n23 ) );
this.y = copySign( this.y, ( m.n13 - m.n31 ) );
this.z = copySign( this.z, ( m.n21 - m.n12 ) );
this.normalize();
return this;
},
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